After undergoing a colostomy or ileostomy operation, the patient is fitted with a disposable bag which receives the waste contents of the intestine. The bag is disposable and is emptied or replaced at regular intervals. To avoid the bag becoming over inflated by virtue of gas generated by the fermenting food matter, it is desirable to provide a vent. However, the vent requires to be filtered in order to prevent embarrassing smells being released.
It is currently conventional practise in colostomy bags to provide an activated charcoal filter in the form of a disc as the vent. For example the disc may have a diameter of 23.5 mm and be formed of activated carbon contained within a foamed polyurethane material, having polypropylene net facings on either or both sides to improve its strength and other mechanical properties. However, this conventional filter material has the significant disadvantage of being liquid-permeable, so that if the patient sits or lies down there is a significant danger of leakage of liquid through the filter onto the patient's skin or his clothing. This is particularly the case with ileostomy bags, where the bag is connected into the early part of the intestine where the food matter is largely undigested and still fermenting, and has a high liquid content. In fact conventional ileostomy bags are not provided with vents, and the filters used for colostomy bags would be quickly saturated with liquid if used for ileostomy.
A porous polytetrafluoroethylene structure containing active carbon is disclosed in our British patent application GB2242431. However, the material disclosed is insufficiently gas permeable.
It is an object of the present invention to provide an ostomy filter which mitigates these problems.
Patent specification GB 1399213 discloses a gas-permeable liquid impermeable membrane which includes finely divided high surface area carbon for the production of hydrogen peroxide.